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The typical image of migration is of northern landbirds, such as swallows and birds of prey, making long flights to the tropics. Many northern-breeding ducks, geese and swans are also long-distance migrants, but need only to move from their Arctic breeding grounds far enough south to escape frozen waters. Most Holarctic wildfowl species remain in the Northern Hemisphere, but in countries with milder climates. For example, the pink-footed goose migrates from Iceland to Britain and neighbouring countries. Migratory routes and wintering grounds are traditional and learned by young during their first migration with their parents. Some ducks, such as the Garganey, move completely or partially into the tropics.
The same considerations about barriers and detours that apply to long-distance land-bird migration apply to water birds, but in reverse: a large area of land without bodies of water that offer feeding sites is a barrier to a water bird. Open sea may also be a barrier to a bird that feeds in coastal waters. Detours avoiding such barriers are observed: for example, Brent Geese migrating from the Taymyr Peninsula to the Wadden Sea travel via the White Sea coast and the Baltic Sea rather than directly across the Arctic Ocean and northern Scandinavia.

Bar-tailed Godwit


A similar situation occurs with waders (called "shorebirds" in North America). Many species, such as Dunlin and Western Sandpiper, undertake long movements from their Arctic breeding grounds to warmer locations in the same hemisphere, but others such as Semipalmated Sandpiper travel longer distances to the tropics in the Southern Hemisphere. Like the large and powerful wildfowl, the waders are strong fliers. This means that birds wintering in temperate regions have the capacity to make further shorter movements in the event of particularly inclement weather.
For some species of waders, migration success depends on the availability of certain key food resources at stopover points along the migration route. This gives the migrants an opportunity to "refuel" for the next leg of the voyage. Some examples of important stopover locations are the Bay of Fundy and Delaware Bay.
Some Bar-tailed Godwits have the longest known non-stop flight of any migrant, flying 11,000 km from Alaska to their New Zealand non-breeding areas.[17] Prior to migration, 55 percent of their bodyweight is stored fat to fuel this uninterrupted journey.

Arctic Terns


Seabird migration is similar in pattern to those of the waders and waterfowl. Some, such as the Black Guillemot and some gulls, are quite sedentary; others, such as most terns and auks breeding in the temperate northern hemisphere, move varying distances south in the northern winter. The Arctic Tern has the longest-distance migration of any bird, and sees more daylight than any other, moving from its Arctic breeding grounds to the Antarctic non-breeding areas. One Arctic Tern, ringed (banded) as a chick on the Farne Islands off the British east coast, reached Melbourne, Australia in just three months from fledging, a sea journey of over 22,000 km (14,000 miles). A few seabirds, such as Wilson's Petrel and Great Shearwater, breed in the southern hemisphere and migrate north in the southern winter. Seabirds have the additional advantage of being able to feed during migration over open waters.
The most pelagic species, mainly in the 'tubenose' order Procellariiformes, are great wanderers, and the albatrosses of the southern oceans may circle the globe as they ride the "roaring forties" outside the breeding season. The tubenoses spread widely over large areas of open ocean, but congregate when food becomes available. Many are also among the longest-distance migrants; Sooty Shearwaters nesting on the Falkland Islands migrate 14,000 km (9,000 miles) between the breeding colony and the North Atlantic Ocean off Norway. Some Manx Shearwaters do this same journey in reverse. As they are long-lived birds, they may cover enormous distances during their lives; one record-breaking Manx Shearwater is calculated to have flown 8 million km (5 million miles) during its over-50 year lifespan.

Griffon Vulture soaring


Some large broad-winged birds rely on thermal columns of rising hot air to enable them to soar. These include many birds of prey such as vultures, eagles, and buzzards, but also storks. These birds migrate in the daytime. Migratory species in these groups have great difficulty crossing large bodies of water, since thermals only form over land, and these birds cannot maintain active flight for long distances. The Mediterranean and other seas present a major obstacle to soaring birds, which must cross at the narrowest points. Massive numbers of large raptors and storks pass through areas such as Gibraltar, Falsterbo, and the Bosphorus at migration times. More common species, such as the Honey Buzzard, can be counted in hundreds of thousands in autumn. Other barriers, such as mountain ranges, can also cause funnelling, particularly of large diurnal migrants. This is a notable factor in the Central American migratory bottleneck.

Ruby-throated Hummingbird


Many of the smaller insectivorous birds including the warblers, hummingbirds and flycatcher[disambiguation needed]s migrate large distances, usually at night. They land in the morning and may feed for a few days before resuming their migration. The birds are referred to as passage migrants in the regions where they occur for short durations between the origin and destination.[18]
Nocturnal migrants minimize predation, avoid overheating, and feed during the day.[16] One cost of nocturnal migration is the loss of sleep. Migrants may be able to alter their quality of sleep to compensate for the loss.[19]
Short-distance and altitudinal migration


Cedar Waxwing


Many long-distance migrants appear to be genetically programmed to respond to changing day length. Species that move short distances, however, may not need such a timing mechanism, and may move in response to local weather conditions.
Thus mountain and moorland breeders, such as Wallcreeper and White-throated Dipper, may move only altitudinally to escape the cold higher ground. Other species such as Merlin and Skylark will move further to the coast or to a more southerly region. Species like the Chaffinch are not migratory in Britain, but will move south or to Ireland in very cold weather.
Short-distance passerine migrants have two evolutionary origins. Those that have long-distance migrants in the same family, such as the Chiffchaff, are species of southern hemisphere origins that have progressively shortened their return migration to stay in the northern hemisphere.
Species that have no long-distance migratory relatives, such as the waxwings, are effectively moving in response to winter weather, rather than enhanced breeding opportunities.

Woodland Kingfisher


In the tropics there is little variation in the length of day throughout the year, and it is always warm enough for a food supply (although because of competition, there may not be enough food for every bird). Migration within the tropics has been far less studied than in the temperate zones. It was once assumed that tropical birds were mostly sedentary; however, altitudinal migration and other within-tropics movements appear to be surprisingly common (citation needed). Many tropical regions have wet and dry seasons, inducing some birds to migrate or wander widely to find food. Indeed, the monsoons of India are preceded by the arrival of the Jacobin Cuckoo, the "harbinger of the monsoon". Other examples include the Woodland Kingfisher of west Africa and many Australian birds.
There are a few species, notably cuckoos, which are genuine long-distance migrants within the tropics. An example is the Lesser Cuckoo, which breeds in India and spends the non-breeding season in Africa. Such examples help make the case that food supplies, not weather per se, drive migration patterns.
Altitudinal migration is common on mountains worldwide, such as in the Himalayas and the Andes. Quite often, altitudinal migration is combined with distance migration; for example, the Himalayan Kashmir Flycatcher and Pied Thrush both move as far south as the highlands of Sri Lanka. Altitudinal migration may even be important to birds living on relatively small islands, such as the Hawaiian Islands, which have high mountains.